1. Field of the Invention
The present invention relates to a sealant hardening apparatus of a liquid crystal display panel (LCD panel), and more particularly, to a sealant hardening apparatus, of an LCD panel and a sealant hardening method thereof being easily applied to LCD panels of the different models, which is suitable for decreasing a tact time by irradiating UV rays in a scanning method, or by directly irradiating UV rays to a sealant pattern without using a mask.
2. Discussion of the Related Art
In the related art liquid crystal display (LCD) device, data signals are provided to individual liquid crystal cells arranged in a matrix-type configuration according to video information. Thus, the LCD device displays a desired image by controlling light transmittance of the liquid crystal cells.
The LCD device includes an LCD panel for displaying a picture image and a driving part for applying a driving signal to the LCD panel. The LCD panel includes first and second glass substrates bonded to each other at a predetermined interval, and a liquid crystal layer having an anisotropic dielectric constant being injected between the first and second glass substrates. Accordingly, the desired image is displayed in the LCD device by controlling the light transmittance through the substrate. The light transmittance is controlled by applying an electric field to the liquid crystal having the anisotropic dielectric constant, and varying the strength of that electric field.
The first glass substrate (TFT array substrate) includes a plurality of gate and data lines, a plurality of pixel electrodes, and a plurality of thin film transistors. The plurality of gate lines are formed on the first glass substrate in one direction at fixed intervals, and the plurality of data lines are formed at fixed intervals in a direction perpendicular to the plurality of gate lines. Then, the plurality of pixel electrodes are respectively formed as a matrix-type configuration in pixel regions defined by crossings of the plurality of gate and data lines. The plurality of thin film transistors are switched according to signals of the gate lines triggering the transmitting of signals of the data lines to the respective pixel electrodes.
The second glass substrate (color filter substrate) includes a black matrix layer that excludes light from portions other than the pixel regions of the first substrate; red (R), green (G), and blue (B) color filter layers for displaying various colors, and a common electrode for obtaining the picture image.
Then, the two substrates are bonded to each other by a sealant, maintaining a predetermined space between the two substrates with spacers, and the liquid crystal layer is formed between the two substrates. Accordingly, as turn-on signals are sequentially applied to the gate lines, data signals are applied to the pixel electrode of the corresponding line, thereby displaying the picture image.
A related art LCD panel will be described with reference to the accompanying drawings.
FIG. 1 is an exemplary view of a unit LCD panel having a thin film transistor array substrate and a color filter substrate bonded to each other. Referring to FIG. 1, an LCD panel 10 includes a lower substrate 1 and an upper substrate 2 bonded to each other at a predetermined interval by a sealant 16, and a liquid crystal layer (not illustrated) formed between the lower and upper substrates 1 and 2. Also, the lower substrate 1 includes an active region 13 having liquid crystal cells arranged in a matrix-type configuration, a gate pad part 14 connected with gate lines of the active region 13, and a data pad part 15 connected with the data lines of the active region 13.
The lower substrate 1, which includes a margin region, is larger than the second substrate 2. The gate pad part 14 and the data pad part 15 are formed in the margin region of the lower substrate 1, wherein the margin region of the lower substrate 1 does not overlap with the second substrate 2. In addition, the gate pad part 14 interfaces a scanning signal provided from a gate driver IC with the gate lines of the active region 13, and the data pad part 15 interfaces a video signal provided from a data driver IC with the data lines of the active region 13.
On the lower substrate 1 of the active region 13, the gate line 3 is provided in perpendicular to the data line 4, so as to define a pixel region, wherein the video signal is applied to the data line 4, and the scanning signal is applied to the gate line 3. Then, a pixel electrode (not illustrated) is formed in each pixel region. A thin film transistor is formed at a crossing of the gate and data lines 3 and 4, respectively, wherein the thin film transistor applies the video signal of the data line 4 to the pixel electrode according to the scanning signal of the gate line 3.
On the upper substrate 2 of the active region 13, there are a black matrix layer (not illustrated) that prevents light on portions except the pixel regions, a color filter layer (not illustrated) that realizes various colors corresponding to the respective pixel regions, and a common electrode (not illustrated).
As described above, the lower and upper substrates 1 and 2 are spaced apart from each other by spacer (not illustrated), thereby forming a cell gap between the lower and upper substrates 1 and 2. Then, the lower and upper substrate 1 and 2 are bonded to each other by a sealant 16 in the periphery of the active region 13, and the liquid crystal layer is formed between the lower and upper substrates 1 and 2 to complete the unit LCD panel.
The liquid crystal layer may be formed in a liquid crystal injection method or a liquid crystal dispensing method.
In the liquid crystal injection method, the two substrates bonded by the sealant are maintained in a vacuum state and an inlet formed in the sealant is dipped into a vessel of liquid crystal, whereby the liquid crystal is injected between the two substrates by capillary action. The inlet is sealed after injection of the liquid crystal. However, the liquid crystal injection method has the problem of low yield because a significant period of time is required to inject the liquid crystal between the two substrates. Also, for fabricating a large-sized LCD panel, the liquid crystal may be incompletely injected between the two substrates, causing defects on the LCD panel.
Accordingly, a liquid crystal dispensing method has been researched and developed, in which the appropriate amount of liquid crystal is dispensed on the lower substrate or the upper substrate before bonding the two substrates to each other.
As explained above, in the liquid crystal injection method, the liquid crystal is injected between the lower and upper substrates after bonding the two substrates to each other by the sealant. Meanwhile, in the liquid crystal dispensing method, the liquid crystal is dispensed on any one substrate before bonding the lower and upper substrates to each other, and then when dispensing is complete the two substrates are bonded to each other. Thus, the liquid crystal injection method requires the inlet provided in a sealant pattern thereof, but the liquid crystal dispensing method requires no such inlet.
FIG. 1 shows the LCD panel of the liquid crystal injection method, which has the inlet in the sealant 16.
A method for fabricating the LCD panel of the liquid crystal injection method will be described as follows.
After designing the plurality of LCD panels on the substrate that is larger than one unit LCD panel, the thin film transistor array is formed on the portion corresponding to each LCD panel of the lower substrate 1, and the color filter array is formed on the portion corresponding to each LCD panel of the upper substrate 2.
Subsequently, an alignment layer is formed to align the liquid crystal in the LCD panel of the lower and upper substrates 1 and 2, and the alignment layer is rubbed. Then, the sealant is formed in the periphery of the LCD panel of the lower substrate 1, spacers are scattered on each LCD panel and the opposite lower and upper substrates 1 and 2 are bonded to each other by the sealant.
After that, the sealant is hardened thereby maintaining the cell gap between the bonded two substrates. Then, the bonded substrates are cut into the LCD panels, and the liquid crystal is injected into each LCD panel, whereby the liquid crystal layer is formed between the lower substrate 1 of the thin film transistor array and the upper substrate 2 of the color filter array, and the inlet for injection of the liquid crystal is sealed.
A method for fabricating the LCD panel of the liquid crystal dispensing method will be described as follows.
After designing the plurality of LCD panels on the substrate that is larger than one unit LCD panel, the thin film transistor array is formed on the portion corresponding to each LCD panel of the lower substrate 1, and the color filter array is formed on the portion corresponding to each LCD panel of the upper substrate 2.
Subsequently, a column spacer for maintaining the cell gap and an alignment layer for aligning the liquid crystal are formed in the LCD panel of the lower or upper substrate 1 or 2, and then the alignment layer is rubbed. After that, the sealant is formed in the periphery of the LCD panel of the first substrate 1 to bond the lower and upper substrates to each other, and the appropriate amount of liquid crystal is dispensed on the LCD panel. Then, the lower and upper substrates are bonded to each other by the sealant. Thereafter, the sealant is hardened, thereby maintaining the cell gap between the bonded two substrates, and the bonded substrates are cut into the LCD panels.
As explained above, in order to fabricate the unit LCD panel, it requires the process of forming the thin film transistor array and the color filter array on the different substrates, forming the sealant 16 in the periphery of the active region 13 so as to bond the lower substrate 1 of the thin film transistor array 1 and the upper substrate 2 of the color filter array, and hardening the sealant.
A method of forming the sealant 16 and a method of hardening the sealant 16 will be described in detail.
FIG. 2A and FIG. 2B are exemplary views of a screen-printing method for forming the sealant according to the related art. As illustrated in FIG. 2A and FIG. 2B, the screen-printing method requires a screen mask 6 and a squeegee 8. At this time, the screen mask 6 is patterned to selectively expose portions of a plurality of sealant patterns 16a to 16c. Also, the squeegee 8 forms the plurality of sealant patterns 16a to 16c by selectively providing the sealant 16 to the substrate 1 through the screen mask 6.
The sealant patterns 16a to 16c are provided on the substrate 1 to obtain a gap for the liquid crystal layer, and to prevent the liquid crystal from leaking to the external of the active regions 13a to 13c. Accordingly, the plurality of sealant patterns 16a to 16c are provided in the periphery of the active region 13a to 13c of the substrate 1. In the liquid crystal injection method, the inlets 5a to 5c is provided at one side for injection of liquid crystal. In the liquid crystal dispensing method, the inlet is not required.
The screen-printing method includes the sequential process of coating the sealant 16 on the screen mask 6 having the plurality of sealant patterns 16a to 16c patterned therein, forming the plurality of sealant patterns 16a to 16c on the substrate 1 by printing with the squeegee 8, and leveling by drying solvent of the sealant patterns 16a to 16c. 
The screen-printing method is common because of its simpler fabrication process. However, the screen-printing method has disadvantages in that a great amount of sealant 16 is used because the plurality of sealant patterns 16a to 16c are formed using the squeegee 8 to coat the sealant 16 on the entire surface of the screen mask 6.
Also, the screen mask 6 is in contact with the substrate 1, so the alignment layer (not illustrated) of the substrate 1 may have defects, thereby deteriorating the picture quality of the LCD device. In order to overcome the problem of the screen-printing method, a sealant dispensing method has been developed.
FIG. 3 is an exemplary view of the sealant dispensing method for forming the sealant pattern according to the related art. As illustrated in FIG. 3, a table 20 on which the substrate 1 is loaded is movable in all directions. In this state, a predetermined pressure is applied to a plurality of syringes 22a to 22c arranged and fixed by a support 21, thereby dispensing the sealant. As a result, the plurality of sealant patterns 16a to 16c are formed along the periphery of the active region 13a to 13c of the substrate 1.
In the sealant dispensing method, the sealant is selectively provided in the periphery of the active region 13a to 13c of the substrate 1, thereby decreasing the sealant consumption. Also, the plurality of syringes 22a to 22c are not in contact with the active region 13a to 13c of the substrate 1, so that it is possible to prevent the alignment layer (not illustrated) from having the rubbing defect, thereby enhancing the picture quality of the LCD device.
In FIG. 2A, FIG. 2B, and FIG. 3, the sealant is a UV and thermal hardening type sealant.
A method of hardening the sealant according to the related art will be described as follows.
FIG. 4 is an exemplary view of a related art sealant hardening method with UV rays. That is, the lower and upper substrates 1 and 2 bonded by the UV hardening type sealant are loaded on a stage (not illustrated) of a container (not illustrated) for the hardening process. Then, a mask 31 is positioned above the lower and upper substrates 1 and 2 bonded to each other, wherein the mask 31 has an open part 31a corresponding to a portion of the sealant 16 through which light is transmitted, and a closed part 31b corresponding to the remaining portions except the sealant 16 to prevent the light.
By aligning the substrates 1 and 2 and the mask 31, the open part 31a is aligned to correspond with the sealant 16, thereby driving a UV irradiation apparatus 30. As a result, UV rays are irradiated onto the sealant 16 of the bonded substrates 1 and 2 through the open part 31a of the mask 31. The UV irradiation apparatus 30 is fixedly provided. Also, the UV irradiation time may be slightly different according to the size of LCD panel. Generally, the UV rays are irradiated in about 30 seconds.
After completing the UV irradiation process of the bonded substrates, a cell cutting process may be employed. If the sealant used is of a UV and thermal hardening type resin, a thermal hardening process may be employed.
However, the related art method of hardening the sealant with UV rays has a number of disadvantages, such as the following.
First, the sealant is hardened with the mask having an open part and a closed part, so an additional mask is required depending on the model of the LCD panel. Also, because it is necessary to align the mask and the bonded substrates, the fabrication cost increases due to the long tact time required.
Furthermore, by fixedly providing the UV irradiation apparatus, the UV rays are irradiated about 30 seconds so as to harden the sealant. That requires a relatively long tact time, thereby lowering the yield.